/*
 * @(#)FunctionBase.java
 *
 * Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.cond;

import org.wso2.balana.ctx.EvaluationCtx;
import org.wso2.balana.Indenter;

import org.wso2.balana.attr.AttributeValue;

import org.wso2.balana.ctx.Status;

import java.net.URI;
import java.net.URISyntaxException;

import java.io.OutputStream;
import java.io.PrintStream;

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

/**
 * An abstract utility superclass for functions. Supplies several useful
 * methods, making it easier to implement a <code>Function</code>. You can
 * extend this class or implement <code>Function</code> directly, depending on
 * your needs.
 * 
 * @since 1.0
 * @author Steve Hanna
 * @author Seth Proctor
 */
public abstract class FunctionBase implements Function {

	/**
	 * The standard namespace where all XACML 1.0 spec-defined functions live
	 */
	public static final String FUNCTION_NS = "urn:oasis:names:tc:xacml:1.0:function:";

	/**
	 * The standard namespace where all XACML 2.0 spec-defined functions live
	 */
	public static final String FUNCTION_NS_2 = "urn:oasis:names:tc:xacml:2.0:function:";

	/**
	 * The standard namespace where all XACML 3.0 spec-defined functions live
	 */
	public static final String FUNCTION_NS_3 = "urn:oasis:names:tc:xacml:3.0:function:";

	// A List used by makeProcessingError() to save some steps.
	private static List processingErrList = null;

	// the name of this function
	private String functionName;

	// the id used by this function
	private int functionId;

	// the return type of this function, and whether it's a bag
	private String returnType;
	private boolean returnsBag;

	// flag that tells us which of the two constructors was used
	private boolean singleType;

	// parameter data if we're only using a single type
	private String paramType;
	private boolean paramIsBag;
	private int numParams;
	private int minParams;

	// paramater data if we're using different types
	private String[] paramTypes;
	private boolean[] paramsAreBags;

	/**
	 * Constructor that sets up the function as having some number of parameters
	 * all of the same given type. If <code>numParams</code> is -1, then the
	 * length is variable
	 * 
	 * @param functionName
	 *            the name of this function as used by the factory and any XACML
	 *            policies
	 * @param functionId
	 *            an optional identifier that can be used by your code for
	 *            convenience
	 * @param paramType
	 *            the type of all parameters to this function, as used by the
	 *            factory and any XACML documents
	 * @param paramIsBag
	 *            whether or not every parameter is actually a bag of values
	 * @param numParams
	 *            the number of parameters required by this function, or -1 if
	 *            any number are allowed
	 * @param returnType
	 *            the type returned by this function, as used by the factory and
	 *            any XACML documents
	 * @param returnsBag
	 *            whether or not this function returns a bag of values
	 */
	public FunctionBase(String functionName, int functionId, String paramType,
			boolean paramIsBag, int numParams, String returnType,
			boolean returnsBag) {
		this(functionName, functionId, returnType, returnsBag);

		singleType = true;

		this.paramType = paramType;
		this.paramIsBag = paramIsBag;
		this.numParams = numParams;
		this.minParams = 0;
	}

	/**
	 * Constructor that sets up the function as having some number of parameters
	 * all of the same given type. If <code>numParams</code> is -1, then the
	 * length is variable, and then <code>minParams</code> may be used to
	 * specify a minimum number of parameters. If <code>numParams</code> is not
	 * -1, then <code>minParams</code> is ignored.
	 * 
	 * @param functionName
	 *            the name of this function as used by the factory and any XACML
	 *            policies
	 * @param functionId
	 *            an optional identifier that can be used by your code for
	 *            convenience
	 * @param paramType
	 *            the type of all parameters to this function, as used by the
	 *            factory and any XACML documents
	 * @param paramIsBag
	 *            whether or not every parameter is actually a bag of values
	 * @param numParams
	 *            the number of parameters required by this function, or -1 if
	 *            any number are allowed
	 * @param minParams
	 *            the minimum number of parameters required if
	 *            <code>numParams</code> is -1
	 * @param returnType
	 *            the type returned by this function, as used by the factory and
	 *            any XACML documents
	 * @param returnsBag
	 *            whether or not this function returns a bag of values
	 */
	public FunctionBase(String functionName, int functionId, String paramType,
			boolean paramIsBag, int numParams, int minParams,
			String returnType, boolean returnsBag) {
		this(functionName, functionId, returnType, returnsBag);

		singleType = true;

		this.paramType = paramType;
		this.paramIsBag = paramIsBag;
		this.numParams = numParams;
		this.minParams = minParams;
	}

	/**
	 * Constructor that sets up the function as having different types for each
	 * given parameter.
	 * 
	 * @param functionName
	 *            the name of this function as used by the factory and any XACML
	 *            policies
	 * @param functionId
	 *            an optional identifier that can be used by your code for
	 *            convenience
	 * @param paramTypes
	 *            the type of each parameter, in order, required by this
	 *            function, as used by the factory and any XACML documents
	 * @param paramIsBag
	 *            whether or not each parameter is actually a bag of values
	 * @param returnType
	 *            the type returned by this function, as used by the factory and
	 *            any XACML documents
	 * @param returnsBag
	 *            whether or not this function returns a bag of values
	 */
	public FunctionBase(String functionName, int functionId,
			String[] paramTypes, boolean[] paramIsBag, String returnType,
			boolean returnsBag) {
		this(functionName, functionId, returnType, returnsBag);

		singleType = false;

		this.paramTypes = paramTypes;
		this.paramsAreBags = paramIsBag;
	}

	/**
	 * Constructor that sets up some basic values for functions that will take
	 * care of parameter checking on their own. If you use this constructor for
	 * your function class, then you must override the two check methods to make
	 * sure that parameters are correct.
	 * 
	 * @param functionName
	 *            the name of this function as used by the factory and any XACML
	 *            policies
	 * @param functionId
	 *            an optional identifier that can be used by your code for
	 *            convenience
	 * @param returnType
	 *            the type returned by this function, as used by the factory and
	 *            any XACML documents
	 * @param returnsBag
	 *            whether or not this function returns a bag of values
	 */
	public FunctionBase(String functionName, int functionId, String returnType,
			boolean returnsBag) {
		this.functionName = functionName;
		this.functionId = functionId;
		this.returnType = returnType;
		this.returnsBag = returnsBag;
	}

	/**
	 * Returns the full identifier of this function, as known by the factories.
	 * 
	 * @return the function's identifier
	 * 
	 * @throws IllegalArgumentException
	 *             if the identifier isn't a valid URI
	 */
	public URI getIdentifier() {
		// this is to get around the exception handling problems, but may
		// change if this code changes to include exceptions from the
		// constructors
		try {
			return new URI(functionName);
		} catch (URISyntaxException use) {
			throw new IllegalArgumentException("invalid URI");
		}
	}

	/**
	 * Returns the name of the function to be handled by this particular object.
	 * 
	 * @return the function name
	 */
	public String getFunctionName() {
		return functionName;
	}

	/**
	 * Returns the Identifier of the function to be handled by this particular
	 * object.
	 * 
	 * @return the function Id
	 */
	public int getFunctionId() {
		return functionId;
	}

	/**
	 * Returns the same value as <code>getReturnType</code>. This is here to
	 * support the <code>Expression</code> interface.
	 * 
	 * @return the return type
	 */
	public URI getType() {
		return getReturnType();
	}

	/**
	 * Get the attribute type returned by this function.
	 * 
	 * @return a <code>URI</code> indicating the attribute type returned by this
	 *         function
	 */
	public URI getReturnType() {
		try {
			return new URI(returnType);
		} catch (Exception e) {
			return null;
		}
	}

	/**
	 * Returns true if this function returns a bag of values.
	 * 
	 * @return true if the function returns a bag, false otherwise
	 */
	public boolean returnsBag() {
		return returnsBag;
	}

	/**
	 * Returns the return type for this particular object.
	 * 
	 * @return the return type
	 */
	public String getReturnTypeAsString() {
		return returnType;
	}

	/**
	 * Create an <code>EvaluationResult</code> that indicates a processing error
	 * with the specified message. This method may be useful to subclasses.
	 * 
	 * @param message
	 *            a description of the error (<code>null</code> if none)
	 * @return the desired <code>EvaluationResult</code>
	 */
	protected static EvaluationResult makeProcessingError(String message) {
		// Build up the processing error Status.
		if (processingErrList == null) {
			String[] errStrings = { Status.STATUS_PROCESSING_ERROR };
			processingErrList = Arrays.asList(errStrings);
		}
		Status errStatus = new Status(processingErrList, message);
		EvaluationResult processingError = new EvaluationResult(errStatus);

		return processingError;
	}

	/**
	 * Evaluates each of the parameters, in order, filling in the argument array
	 * with the resulting values. If any error occurs, this method returns the
	 * error, otherwise null is returned, signalling that evaluation was
	 * successful for all inputs, and the resulting argument list can be used.
	 * 
	 * @param params
	 *            a <code>List</code> of <code>Evaluatable</code> objects
	 *            representing the parameters to evaluate
	 * @param context
	 *            the representation of the request
	 * @param args
	 *            an array as long as the params <code>List</code> that will, on
	 *            return, contain the <code>AttributeValue</code>s generated
	 *            from evaluating all parameters
	 * 
	 * @return <code>null</code> if no errors were encountered, otherwise an
	 *         <code>EvaluationResult</code> representing the error
	 */
	protected EvaluationResult evalArgs(List<Evaluatable> params,
			EvaluationCtx context, AttributeValue[] args) {
		Iterator it = params.iterator();
		int index = 0;

		while (it.hasNext()) {
			// get and evaluate the next parameter
			Evaluatable eval = (Evaluatable) (it.next());
			EvaluationResult result = eval.evaluate(context);

			// If there was an error, pass it back...
			if (result.indeterminate()) {
				return result;
			}
			// ...otherwise save it and keep going
			args[index++] = result.getAttributeValue();
		}

		// if no error occurred then we got here, so we return no errors
		return null;
	}

	/**
	 * Default handling of input checking. This does some simple checking based
	 * on the type of constructor used. If you need anything more complex, or if
	 * you used the simple constructor, then you must override this method.
	 * 
	 * @param inputs
	 *            a <code>List></code> of <code>Evaluatable</code>s
	 * 
	 * @throws IllegalArgumentException
	 *             if the inputs won't work
	 */
	public void checkInputs(List inputs) throws IllegalArgumentException {
		// first off, see what kind of function we are
		if (singleType) {
			// first, check the length of the inputs, if appropriate
			if (numParams != -1) {
				if (inputs.size() != numParams)
					throw new IllegalArgumentException("wrong number of args"
							+ " to " + functionName);
			} else {
				if (inputs.size() < minParams)
					throw new IllegalArgumentException("not enough args"
							+ " to " + functionName);
			}

			// now, make sure everything is of the same, correct type
			Iterator it = inputs.iterator();
			while (it.hasNext()) {
				Evaluatable eval = (Evaluatable) (it.next());

				if ((!eval.getType().toString().equals(paramType))
						|| (eval.returnsBag() != paramIsBag))
					throw new IllegalArgumentException("illegal parameter");
			}
		} else {
			// first, check the length of the inputs
			if (paramTypes.length != inputs.size())
				throw new IllegalArgumentException("wrong number of args"
						+ " to " + functionName);

			// now, make sure everything is of the same, correct type
			Iterator it = inputs.iterator();
			int i = 0;
			while (it.hasNext()) {
				Evaluatable eval = (Evaluatable) (it.next());

				if ((!eval.getType().toString().equals(paramTypes[i]))
						|| (eval.returnsBag() != paramsAreBags[i]))
					throw new IllegalArgumentException("illegal parameter");

				i++;
			}
		}
	}

	/**
	 * Default handling of input checking. This does some simple checking based
	 * on the type of constructor used. If you need anything more complex, or if
	 * you used the simple constructor, then you must override this method.
	 * 
	 * @param inputs
	 *            a <code>List></code> of <code>Evaluatable</code>s
	 * 
	 * @throws IllegalArgumentException
	 *             if the inputs won't work
	 */
	public void checkInputsNoBag(List inputs) throws IllegalArgumentException {
		// first off, see what kind of function we are
		if (singleType) {
			// first check to see if we need bags
			if (paramIsBag)
				throw new IllegalArgumentException(functionName + "needs"
						+ "bags on input");

			// now check on the length
			if (numParams != -1) {
				if (inputs.size() != numParams)
					throw new IllegalArgumentException("wrong number of args"
							+ " to " + functionName);
			} else {
				if (inputs.size() < minParams)
					throw new IllegalArgumentException("not enough args"
							+ " to " + functionName);
			}

			// finally check param list
			Iterator it = inputs.iterator();
			while (it.hasNext()) {
				Evaluatable eval = (Evaluatable) (it.next());

				if (!eval.getType().toString().equals(paramType))
					throw new IllegalArgumentException("illegal parameter");
			}
		} else {
			// first, check the length of the inputs
			if (paramTypes.length != inputs.size())
				throw new IllegalArgumentException("wrong number of args"
						+ " to " + functionName);

			// now, make sure everything is of the same, correct type
			Iterator it = inputs.iterator();
			int i = 0;
			while (it.hasNext()) {
				Evaluatable eval = (Evaluatable) (it.next());

				if ((!eval.getType().toString().equals(paramTypes[i]))
						|| (paramsAreBags[i]))
					throw new IllegalArgumentException("illegal parameter");

				i++;
			}
		}
	}

	/**
	 * Encodes this <code>FunctionBase</code> into its XML representation and
	 * writes this encoding to the given <code>OutputStream</code> with no
	 * indentation.
	 * 
	 * @param output
	 *            a stream into which the XML-encoded data is written
	 */
	public void encode(OutputStream output) {
		encode(output, new Indenter(0));
	}

	/**
	 * Encodes this <code>FunctionBase</code> into its XML representation and
	 * writes this encoding to the given <code>OutputStream</code> with
	 * indentation.
	 * 
	 * @param output
	 *            a stream into which the XML-encoded data is written
	 * @param indenter
	 *            an object that creates indentation strings
	 */
	public void encode(OutputStream output, Indenter indenter) {
		PrintStream out = new PrintStream(output);
		out.println(indenter.makeString() + "<Function FunctionId=\""
				+ getFunctionName() + "\"/>");
	}

}
